Image capture devices, such as digital video cameras or digital still cameras, are used in different applications and environments. An image capture device should be capable of producing high quality imagery from a variety of distances relative to a target of a scene. A typical image capture device may perform an auto-focus process to select a position of a lens within the image capture device that achieves a sharp focus for an image frame of the scene. Without proper focus, captured images or video may appear blurry.
An image capture device may perform an active auto-focus process, a passive auto-focus process, or a combination of the two processes. In the case of passive auto-focus, the auto-focus process implemented by an image capture device may calculate a focus value, such as an image sharpness measure, at several sampled lens positions and select the position of the lens for the scene based on the focus values. For example, in the auto-focus process, the image capture device may select the lens position that yields the best focus value. The lens positions evaluated by the auto-focus process may reside within a specified search range.
Moving the lens to multiple lens positions within the search range can result in auto-focus latency and undesirable power consumption. In addition, manufacturing characteristics of lens modules may vary, resulting in differences in auto-focus performance.